Distortion

Typical for most tele zoom lenses the Panasonic produces a low level of distortion. The lens shows slight pincushion distortion (~1%) at 100mm changing to slight barrel distortion at 300mm (~0.3%). This is nothing to worry about in field conditions.

If you move your mouse cursor over the image you can switch to the corresponding non-corrected results.

Vignetting

The super telephoto lens has an average vignetting characteristic. The following figures show the corresponding performance of auto-corrected JPEGs obtained straight from the camera compared to non-corrected raw files.

The focal length between 100 and 200mm shows only slight vignetting. However, at 300mm and wide open aperture the amount of vignetting is very pronounced at ~0,9EV which is easily noticeable in field images. Nevertheless, vignetting it's not really an issue anymore from f/8 onwards. The non-corrected (RAW) images show slightly worse results particularly at 300mm with a heavy amount of vignetting of up to ~1.2EV at f/5.6.

The following graphs compare the vignetting characteristic of auto- and non-corrected files between 100 and 300mm from open aperture to f/11.

The following images illustrate the above mentioned heavy vignetting at 300mm.

MTF (resolution)

The Panasonic lens produced decent but not stellar resolution figures in the MTF lab although this is certainly acceptable considering its huge focal length range. The performance is best at 100mm with a generally good to very good quality across the image field. There's a slight decrease in performance towards 200mm and slightly more so at 300mm.

Below is a simplified summary of the formal findings. The chart shows line widths
per picture height (LW/PH) which can be taken as a measure for sharpness.
If you want to know more about the MTF50 figures you may check out the corresponding
Imatest Explanations

Chromatic Aberrations (CAs)

A good news for Panasonic users is the low amount of lateral CAs (color shadows at harsh contrast transitions) - at least when shooting JPEGs or using mainstream RAW converters. These color shadows are negligible throughout the whole focal length with an average CA width of around ~0.4px at the image borders.

However, the non-corrected RAWS show a completely different situation with an average CA width of around ~1.2px at 200mm and almost 2px at 300mm. These values can be very disturbing on Olympus cameras where the RAWs are not auto-corrected in this respect.
The following figures show the corresponding performance of auto-corrected JPEGs obtained straight from the camera compared to non-corrected raw files.